Positive effect of inaudible high-frequency components of sounds on glucose tolerance: a quasi-experimental crossover study

Figures

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  Figure 1. Averaged glucose response curves during the oral glucose tolerance tests under the three experimental conditions. (a) mean glucose level across 25 participants (b) mean glucose increments from baseline. Error bars indicate standard error of mean. Gray, blue, and pink lines correspond to no sound, high-cut sound, and full-range sound, respectively. A significant main effect of the experimental condition was observed both in the glucose levels and their increments; however no significant interaction was found between time and the experimental condition in either comparison. Between-condition comparisons with Holm’s correction for multiple comparisons showed that the glucose level in the full-range sound condition was significantly lower than that in the high-cut sound condition (P = 0.025). Moreover, the glucose level increments in the full-range sound condition were significantly smaller than those in the high-cut sound (P = 0.000012) and no sound conditions (P = 0.0018).

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  Figure 2. Incremental area under the curve (iAUC) for the three sound conditions for the 25 participants. Red thick line indicates the mean across all participants and error bars indicate the standard error of mean. Colored thin lines indicate each participant’s data. The iAUC was smaller in the full-range sound condition compared with the high-cut sound condition (P = 0.039 with Holm correction for multiple comparisons).

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  Figure 3. Incremental area under the curve (iAUC) for the three sound conditions for the participants grouped by age. Orange indicates the mean and the standard error of mean of 13 participants in the high-age group and green indicates those of 12 participants in the low-age group. Mean age of high-age and low-age groups was 63.3 (59–69) years and 51.3 (42–57) years, respectively. iAUC was significantly smaller in the full-range sound condition than in both the no sound and high-cut sound conditions in the high-age group, whereas this tendency was not observed in the low-age group.

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  Figure 4. Incremental area under the curve (iAUC) for the three sound conditions for the participants grouped by the value of HbA1c. Orange indicates the mean and the standard error of mean of 14 participants in the high-HbA1c group and green indicates those of 11 participants in the low-HbA1c group. Mean HbA1c of high-HbA1c and low-HbA1c groups was 5.80% (5.5–6.5%) and 5.17% (4.5–5.4%), respectively. iAUC was significantly smaller in the full-range sound condition than in the no sound in the high-HbA1c group, whereas this tendency was not observed in the low-HbA1c group.